Diesel mechanics diagnose problems with diesel-powered engines, repair them, perform routine maintenance on them and test them. They might work on city buses, semis or diesel engine automobiles. According to the U.S. Bureau of Labor Statistics, the number of jobs for diesel mechanics should increase 15% during the decade ending in 2020, a slightly higher rate than the average for all occupations. The BLS expects that the best opportunities will go to those with the right qualifications, including formal training and excellent technical skills.

Training and Education

Some employers are willing to hire inexperienced mechanics and train them on the job. They typically start with simple tasks such as checking oil levels, cleaning parts or assisting experienced mechanics. If they train on the job, diesel mechanics can spend as long as four years as a trainee before they can work without close supervision. According to O*Net Online, around 25 percent of the nation's diesel mechanics have some college, but no degree. Approximately 40 percent have earned a high school diploma or equivalency certificate, and 30 percent did not graduate from high school. Because formally trained mechanics typically require less supervision and shorter training periods, the BLS reports that many employers prefer to hire candidates who have earned either a certificate or two-year degree in diesel mechanics. Such programs can last as little as six months or as long as two years, and are normally offered by vocational schools, community colleges and trade schools.

Mechanical Aptitude and Skills

Mechanics need to understand the principles of how vehicles work so they can diagnose and troubleshoot problems. They need to know how to use basic hand tools such as wrenches, tire pressure gauges and screwdrivers, as well as advanced tools such as computerized test equipment, welding torches and hydraulic hoists.

Physical Abilities

Diesel mechanics need good manual dexterity, including the ability to make precise finger movements and the ability to keep their arms and hands steady. They need normal vision and hearing, along with the ability to converse with others. The job often involves stretching, bending or twisting, so mechanics need the strength and stamina to perform tasks without overtaxing their bodies.

Miscellaneous Qualifications

Some diesel mechanics offer roadside assistance, so they need the ability to perform their jobs even if the weather is severe. If they road-test buses or trucks, they may need a commercial driver's license. Although most garages are well ventilated, diesel mechanics can still be exposed to hazardous fumes, so the ability to understand and follow safety procedures is important. Analytical skills are needed to diagnose problems and determine the appropriate steps to fix them. Some mechanics must discuss symptoms or repair options with their customers, so they need adequate customer-service skills. Because most diesel engines have integrated electronic systems, mechanics need sufficient understanding of how these systems work and which tools are needed for tests and repairs.